High pressure booster valve

ABSTRACT

A pneumatic conveyor tube booster valve constructed from an annular tapered rubber sleeve in line with the tube and a sealed pressurized housing surrounding the sleeve portion of the tube. Pressurized gas introduced into the housing escapes past the rubber sleeve when the tube pressure drops below the housing pressure by a predetermined amount and enters the tube in substantially the same direction in which material in the tube is moving. Annular lips on the conveyor tubes supports the rubber sleeve against pressures in the tube.

United States Patent 1191 Steele Jan. 2, 1973 1 HIGH PRESSURE OOS VA V2,897,003 7/1959 Wiltse "302/24 2,265,615 12/1941 Stalter ..277/208 [75]Inventor. James resume, St. Paul, Mmn. 3,065,761 "962 Perasm 137/525 X[73] Assignee: Dynamic Air Inc., Saint Paul, Minn. 2,946,628 9 gg t2,794,686 6/1957 Anselman et al.... .....302/24 Flledl April 16, 19711,733,302 10/1929 Horn ..302/64 x 21 A 1. No.: 134 764 1 pp PrimaryExaminer-Even C. Blunk Related 1.1.8. Application Data AssistantExaminer-W. Scott Carson [63] Continuationin-part of Ser. No. 886,091,Dec. 18, & Jacobson 1969, b d d. 1

a 57 ABSTRACT US. Cl. ..302/24, A pneumatic conveyor tube booster valveconstructed 302/35 from an annular tapered rubber sleeve in line withthe [5 Cl. ..B65g tube and a sealed pressurized housing urrounding theField of Search "137/516-25, 516-29, sleeve portion of the tube.Pressurized gas introduced 137/525 604, 605; 251/145; into the housingescapes past the rubber sleeve when 277/208; 302/24 29 the tube pressuredrops below the housing pressure by a predetermined amount and entersthe tube, in sub- References u stantially the same direction in whichmaterial in the UNITED STATES PATENTS tube is moving. Annular lips onthe conveyor tubes supports the rubber sleeve against pressures in the3,499,461 3/1970 Tuma... ..137/240 tube. 3,539,149 11/1970 Breny........251/145 2,489,715 11/1949 Mark et a1. 77/208 X 7 Claims, 3 DrawingFigures 5s 66 7o f END RECEIVER PATENTEUJAI 2 Ian SHEET 1 OF 2 3.708,207

PRESSURE END SOURCE RECEIVER PRESSURIZED AIR 24 I8 I V o t I 2 E 20 I h30 Y 2 a 32 INVENTOR JAMES 1?. STEELE ATTORNEYS PATENTEUJAN 2197s saw 2[1r 2 ENTOR AMES R. STEELE ATTORNEYS HIGH PRESSURE BOOSTER VALVEBACKGROUND OF THE INVENTION This application is a continuation-in-partof my copending application Ser. No. 886,091, filed Dec. 18, 1969, for aPneumatic Conveyor Booster Valve," in the name of the instant inventor,now abandoned.

Pneumatic conveyors are often employed for a wide variety of conveyorapplications including the transfer of dry granular material such assand, salt, flour, and cement. Two types of systems are in general usefor the transfer of granular materials. The first type depends upon ahigh velocity air stream to carry a relatively small amount of materialat high speeds. Serious disadvantages accompany this method. The highspeed of the particles tends to abrade the interior surfaces of theconveyor tubes. Hence, continual maintenance is a necessity and frequentoperational shutdowns are required to repair and replace parts. Inaddition, the high velocity impacts which are unavoidable in this therubber sleeve so that air introduced into the housing can displace thesleeve and enter the tube when the j pressure in the tube drops belowthe housing pressure type of system destroy the transported material orreduce it to an undesirably low grain size. 7

A preferred type of pneumatic conveyor which avoids the above problemsis the slow speed variety in which the conveyor tube is practically fullof material which material is moved by air pressure applied to it at itssource and at a number of successive locations along the conveyor tube.Although the speed of the material is less, the density is so muchhigher that the net volume moved per unit time is much higher.Furthermore, wear is reduced both on the conveyor tube and on thematerial.

The present invention pertains to the booster valves positioned alongthe conveyor tube which function to add pressure as required to keep thematerial moving. Prior art booster valves are extremely difficult toadjust. If too much pressure is applied, the material in the conveyortube is blocked. On the other hand, if the pressure is too low, thematerial is not properly transported. Since the'proper applied pressuredepends on the pressure inside the tube and since the pressure in thetube varies with the material density, flow rate, consistency, and thepressure applied by adjacent booster valves, it is readily apparent howdifficult it is to achieve the correct pressure. Continual adjustmentsare necessary to maintain the'careful balance of the system. One methodof simplifying this type of pneumatic conveyor system is to employone-way valves in the booster stations which operate to releasepressurized gas into the tube when the pressure in the tube drops belowa predetermined value. However, these valves usually becomeclogged dueto material in the channels leading from the conveyor tubes to the oneway booster valve backing up into the valve before it can close. Thebacked up material soon scores the sealing surfaces and valvereplacement becomes necessary. My invention contemplates an improvedbooster-valve design which avoids the above-mentioned problems.

SUMMARY OF THE INVENTION Briefly, a unique booster valve design iscontemplated which does not clog and which injects air into the conveyortube about the entire circumference of the tube. An annular taperedrubber sleeve is positioned in line with the conveyor tube. A sealedpres- BRIEF DESCRIPTION or THE DRAWING FIG. 1 is a diagrammatic view ofa typical pressurized pneumatic conveyor of the type in which thepresent invention has maximum utility;

' FIG. 2 is a schematic sectional view of one preferred embodiment ofthe present invention; and

FIG. 3 is a schematic sectional view of another preferred embodiment ofmy. invention particularly adapted to withstand large back pressures..

DESCRIPTION or THE PREFERRED EMBODIMENT FIG. 1 demonstrates a typicalpneumatic conveyor system. The material to be transported-is introducedinto a pressurized transporter 40 by a hopper 42 and a surized housingencloses the section of tube containing I butterfly valve 44 which isactivated by an air cylinder 48 or any other suitable apparatus.Transportation is effected by closing .valve 44 andpressurizingutransporter 40with a gas such as air supplied by a source50 through a line 52. The pressurized air pushes the material along apneumatic conveyor tube 54 to any desired location such as a receiver56. As mentioned earlier, this type of system requires-a number ofbooster valves 58, 60 and 62 which add additional air to tube 54 atsuitable successive locations. In the example shown, pressurized airfrom source 50 travels through three manually adjustable valves 64,65and 66,

through three meters 68, 69 and 70, and into the three boostervalves'58, 60 and'62. The uniquedesign of the booster valves of thepresent invention is shown in FIG.

In FIG. 2 conveyor tube 54 is again shown. Tube 54 is divided into twoportions to permit insertion of the valve. The first portion is machinedto have a beveled edge 32 while the second portion is shaped to have anannular lip 30. An annular flexible valve member28 slides over lip 30and extends across to'contact beveled edge 32. Flexible member 28 may beconstructed from a variety of materials, rubber being contemplated forthe preferred embodiment.- Each of the two portions of tube 54 issecured by a suitable collar 12 or 14 which is welded or otherwisefastened to tube 54. An annular ring or tube 20 separates collars l2 and14 while a plurality of bolts such'as bolts 16 and 18 compress collarsl2 and 14 and therefore hold the two portions of tube 54 in place. Inthis way'a'n annular, pressure'tight housing or chamber 26 is formedabout tube 54. Air is introduced into chamber 26-by means of a line24'which, of course, is angled to clear bolt 18. If the pressure inchamber 26 exceeds that insidetube 54 by a sufficient amount, the rubbermember 28 is displaced and air enters tube 54 to help move the materialtherein.

The design described in FIG. 2 possesses a number of advantageous designfeatures which make it far superior to prior art approaches. Material inthe tube moves in the direction indicated by arrow 22. Beveled edge 32and the corresponding face of rubber member 28 insure that air enterstube 54 in substantially the same direction as the flow thus helping theflow and removing any tendency of the material to back up into the airadmission passage. Also, the nature of the valve is such as toprogressively close as the pressure differential decreases. When thepressure differential reaches a predetermined cracking value, theflexible rubber member 28 will resume its natural shape and seal theopening so that rubber valve'28 is compressed tightly against edge 32leaving no holes, slots or ridges upon which material can accumulate.

In the preferred embodiments, cracking pressures of from 1 to Spoundsper square inch have been experienced with the valve disclosed herein.Because of this minimum differential cracking pressure, the valve reallyclosesbefore there is any tendency for the transported material tov backup into housingchamber 26. This is important because the slightestamount of material can operate to hold any'valve open causing a leakbackwards through the valve.

Surface 36presents a smoothcontinuous surface to the moving material sothat the interior dimensional continuity of tube 54 is nearly unbroken.This is especially true in the normal operating mode where a smallamount of air is passing into the tube. Flexible member 28 is shaped andpositioned to approximate the internal dimensions of tube 54 when it isdisplacedto admit air to tubes 54.

Additional important design features include a pair of pressure ridges34, whichencourage a tight seal when flexible valve member 28 is closed,and an annular extended portion 29 which expands'against the walls ofchamber 26 due to pressure in chamber 26 thus firmly holding member 28in place. This holding action is sufficient'to'permit the removal of lip30 in the preferred embodiment. However, this lip' 30 has been shown inFIG. 2 by way of a complete disclosure. It should'be noted thatflexiblemember 28 compresses evenly over its entire circumference whenadmitting air as has been proven by experimentation. This is truebecause the average thickness of the sleeve approximated at'the centerof the'sleeve by the measurementY in FIG. 2is great enough infcomparisonto the unsupported length of the sleeve X to insure that the sleeve hasstrength enough to retain its natural shape. It has been found that ifthe average thickness Y is reduced, flexible'mer'nb'er 28 will buckle infrom the weakest side first admitting air to tube 54 on one side onlywhereas if the average thickness Y is too great, the cracking pressurebecomesftoo large. Another problem that can arise in the prior art isexperienced when clogs or other abnormalities cause a high "pressuresurge in tube 54. These high pressures can bend, flexible member 28 intochamber 26 andclog chamber 26 with material if the Y dimension isinadequate. For ordinary rubber materials the flexible member 28 hasbeen found to work best 6 with the ratio of X to Y being in the range ofabout 1' to 2, for example, is constructed with the ratio of X to Ybeing about 4 to 1. In order to avoid the design limitations of theabove-mentioned ratios and still have the proper cracking pressurecharacteristics, the embodiment of FIG. 3 is useful although requiringmore ,complicated castings. g g I In FIG. 3 a conveying tube is providedwith interlocking or overlapping annular lips 81 and Pressurized air isintroduced into annular housing 83 from a tube 84 where the air canreach the back side of array; lar flexible valve member 85 through aseries of circumferentially spaced holes 86. Any number of holes simplyoperate to seal flexible member 85 tightly against lip 81. Thus, athinner valve member 85 may be utilized. Experimentation has proven thatthe ratio of the area of the sealing surface between flexible member 85and annular lip 81 measured across the length of tube opening defined bythe letter A in FIG. 3, to the total area of the spaced holes 86 shouldlie in the range of about 10 to I up to about 500 to l. Thepreferredembodiment contemplated by FIG. 3 has a ratio-of about 30 to l, but thisratio may be varied as desired to control the cracking pressure so as toinsure against any backingup of the conveyed granular materialinto thevalve sealing area. I

lclaim: 7 1. Inpneumatic conveying apparatus a booster valve incombination with a conveying tube comprising: 1 f

a pressure tight housing disposed about the tube in t fluidcommunication with the'inside of the tube by means of an opening throughthe wall of the tube; a generally annular flexible 'member'coverin g thetubeop'ening; Y a rigid annular lip extending over the length of th 7tube opening surrounding said flexible member for therefor against backpressures flow from said tube into said housing; and

a source of fluid pressure connected to said housing I I adapted I topresent a substantially constant predetermined pressure to saidpassageways.

' 2. The apparatus of claim 5 in which the outersur-' face of saidflexible member is taperedso that said flex ing displacement opens apath from the passageways to the tube opening which ,is generally inthedirection of flow ofmaterial in said tube. v 1

' 3. The apparatus of claim 2 includingat least one pressure ridge onthe tube contacting surface of said flexible membe'roperable to insure atight seal between said tube and said flexible member.

4. The apparatus of claim 2 i in which-said passageways comprise aplurality of holes arranged l up'to about 6'to l. The preferredembodiment of FIG. .the tapered surface of said flexible member. 7 1

tube by a predetermined amount butresistant to over the length of thetube opening to the area of said plurality of holes lies in the range ofabout 10 to l to about 500 to l.

7. The apparatus of claim 6 in which said ratio is about 30 to l.

I a: a a: :r

1. In pneumatic conveying apparatus a booster valve in combination witha conveying tube comprising: a pressure tight housing disposed about thetube in fluid communication with the inside of the tube by means of anopening through the wall of the tube; a generally annular flexiblemember covering the tube opening; a rigid annular lip extending over thelength of the tube opening surrounding said flexible member forproviding support therefor against back pressures in the tube;passageways through said lip; said flexible member operable by means ofpressure induced flexing displacement to permit the flow of fluid fromsaid passageways into said tube if the pressure in the housing exceedsthe pressure in the tube by a predetermined amount but resistant to flowfrom said tube into said housing; and a source of fluid pressureconnected to said housing adapted to present a substantially constantpredetermined pressure to said passageways.
 2. The apparatus of claim 5in which the outer surface of said flexible member is tapered so thatsaid flexing displacement opens a path from the passageways to the tubeopening which is generally in the direction of flow of material in saidtube.
 3. The apparatus of claim 2 including at least one pressure ridgeon the tube contacting surface of said flexible member operable toinsure a tight seal between said tube and said flexible member.
 4. Theapparatus of claim 2 in which said passageways comprise a plurality ofholes arranged generally orthogonal to the flow of material in said tubethrough which fluid passes from said housing against the tapered surfaceof said flexible member.
 5. The apparatus of claim 4 in which saidannular lip extends beyond the length of the tube opening so as tooverlap an end of the tube with said annular flexible membertherebetween.
 6. The apparatus of claim 5 in which the ratio of the areaof said annular lip supporting said flexible member over the length ofthe tube opening to the area of said plurality of holes lies in therange of about 10 to 1 to about 500 to
 1. 7. The apparatus of claim 6 inwhich said ratio is about 30 to